“Nevertheless, our society has a duty to protect the very worst in society as well as the very best. This was a significant attack involving terrible violence.

“But for good fortune, there could have had been much worse physical consequences.”

Crawford is serving life with an 18-year minimum term after being found guilty of killing Scott Adams, 20, in Clydebank in 2010. He had been due for possible release in September 2028 before yesterday’s sentence.

Crawford admitted attacking Shahid to his severe injury and danger of life.

An earlier hearing was told Shahid had a fractured jaw and cheekbone and shattered teeth. He was attacked by a mob but Crawford was the only one prosecuted.

Prosecutor Bernard Ablett said Shahid was training in the gym when Crawford lifted a 15kg weight.

He said: “He lifted the weight above his head and then struck the top of Shahid’s head from behind, knocking him to the floor.”

Crawford then threw himself on Shahid and stamped on him before other prisoners armed with metal poles battered him.

Shahid and three other men were convicted of murdering Kriss in 2004.

They abducted the teenager from the south side of Glasgow and tortured him before killing him.